Electrical furnace.



H. NATHUSIUS.

ELECTRICAL FURNACE.

APPLICATION FILED JUNE 24, 1909.

Patented Aug. 15, 1911.

INVEN TOFI HANS NATHUSIUS,

ATTORNEYS WI TNES SES'.

IHL A'NS NATHUSIUS, OF FRIEDENSH'U'TTE, NEAR .MORGENROTH GERMANY.

ELECTRICAL FURNACE.

Specification of Letters Patent.

Patented Aug. 15, 1911.

Application filed June 24, 1909. Serial No. 503,988.

To all whom it may concern:

Be it known that I, HANS NATHUSIUS, a subject of the King of Prussia, and residing at Friedenshiitte, near Morgenroth, Ger-.

many, have invented a new and useful Improvement 1n Electrical Furnaces, of which the following is a specification.

This invention relates to a modification of or improvement in the invention described in my co-pending applications Serial Nos. 431,158 and 431,300, filedre spectively being now Patent No. 958,757, and the former being now Patent No. 983,303.

The furnace for electric smelting and refining of metals, more particularly of steel, described in the prior specifications differs from electric furnaces used for the same purpose, by the fact that both on the surface of the bath and at the bottom of the furnaces are arranged several'electrodes of alternat-ing polarity in such manner that the electric current is forced to pass from one surface electrode to another surface electrode, from one surface electrode to an opposite bottom electrode, and from one bottom electrode to another bottom electrode.

' Thus the charge is surrounded by electric currents of suitable heating power. Not

only, therefore, as in old furnaces, either only a portion of the surface of the bat-h, or only the bath itself is heated, but the bulk of the bath and the surface of the bath are properly heated simultaneously. The uniform heating on all sides means not only absence of loss but also quickness of the refining process.

'The object of this invention is to attain uniformity of heating by special devices and connections, with the assistance of which it can be regulated for those stages of the steel process in which at given places and at given times a smaller or stronger heating is required. Specification 431,300 referred to the above point, and its object was to get by means of special methods of connection the eatest heat concentrated on the surface of the bath, or in the metal bath itself according to the state of the charge. For during the fining stage,that is to say, during the refining process, the chief heat is required in the slag zone, more particularly as in the electric steel process the fining is carried out not by means of blast or combustion gases but only with ore. It will be obvious that May 6 and May 7, 1908, the latter durin that period, it is desirable to have the highest possible heating of the slag cover, as the increase of temperature increases also the re-acting capacity of a reagent. stages of the steel process during which refining no longer takes place, that is to say, for instance during the reducing (deoxidizing) or decarbonizing period, it is desirable to have a less strong heating of the same.

In the same way it is of course an advantage at this stage to be able to transfer the chief heating action to the metal bath itself where the main reactions take place. It is even possible to go so far as to switch out alto- It will also be clear that for those gether the surface electrodes at those stages of the steel process, during which chemical reactions take place only in the metal bath, that is to say, during the alloy or tapping periods the chemical composition of the bath is to be equalized and the said bath steadied and in which the slag only forms a protection cover for preventing the access of air to the metal bath, and to admit the currentonly through the bottom electrodes (as already pointed out on page 3 of the specifica-.

tion 431,158). These conditions are fulfilled in a very advantageous manner by providing the furnace according to the prior specification No. 431,158 with the devices herinafter described or using the connection hereinafter described.

While the invention described in the other prior specification, to wit, my application Serial No. 431,300, has for one of its principal objects the deflection of a large portion of the electric current into the surface of the bath, or' in other words into the slag zone, to there form voltaic arcs, this deflection of current being accomplished by means of electrodes which can be disconnected, and also by means of regulating resistances; the present invention has for one of its objects the deflection of a large portion of the current downward into the hearth-sole or mto the metal bath proper without .the use of expensive regulating resistances which 1n some cases destroy energy; or to heat the latter alone by resistance heating with completeexclusion of surface electrodes forming voltaic arcs. I

When using resistance heating,'the metal bath or the hearth sole is heated by means of Joules effect. This depends, as is well known, on the one hand on the resistance of the material itself, throu h which the current is passing and on-tlie other hand, on the strength of the current, and is in proortion to its square. For increasing the iieating action in the bath there are, therefore, available two methods: 1. Increase of the resistance. 2. Increase of the strength of the current. In this invention the increase of the strength of current in the bath itself or in the hearth sole, in a furnace according tothe prior specification No. 431,158 when using three-phase alternating current in accordance with the connections shown in Figure 1 is obtained by dissolving the nodal point of the machine and connecting the three inner ends which otherwise form the neutral point, to the bottom electrodes, while the outer ends are connected in the usual manner to the three surface electrodes. By means of this connection the neutral point is transferred into the metal bath itself, that is to say, the whole current supplied by the source of current, and not only a ortion of it as in the invention described in specification No. 431,300, is forced to pass throughthe Whole metal bath and also through the bottom electrodes. The whole strength of current is, therefore,'utilized for heating the metal bath or the hearth sole. This heating action in the bath or the increase of heating action due to resistance heating in the metal bath or in the hearth sole, by increasing the current, can also be advantageously obtained by con necting in front of the'bottom electrodes a transformer which transforms the current from the main furnace source of current to a very high stren th of'current with a correspondingly snnll pressure, so that. in addition to the primary current a. current of any desired strength is supplied b the bottom electrodes direct to the metal ath or to the hearth sole. The transformer for producing the stron current supplied only b the lower electrodes, is preferably built (1!- rectl under the electric furnace as part of the atter, so that the lower electrodes can .be directly connected to the transformer.

This resu in a saving of copper wire which otherwise forms such a great item of expenditure for such great strength of current.

Instead of a transformer, any other source of current separate from the main source of current and independent of the same could be used for producing the lower electrode current,v or a transformerwith two different windings could be used as a joint. source of current, one winding supplying a secondary high pressure current (such as required for voltaic arc formation) of smallerstrength used as main current and the other winding supplying asecond- .ary current with low pressure and great strength (as required for obtaining the Joules effect by means of strength of current) used as bottom electrode current.

Referring to the accompanying drawings which form a part of this specification: Fig. 1 is a diagramn'iatic representation of an electric furnace operating in accordance with the principles hereinbefore set forth. Fi 2 is a diagrammatic representation of a urnacc showing a modification of electric connections thereto. Fig. 3 is a section of furnaceshowing a lining formed ofa conductor of the second class disposed around and over the inner extremities of the bottom electrodes.

The upper electrodes have respectively been designated a, 7) and 0 throughout the. several views, and the bottom electrodes at, e and f, in corresponding fashion.

Referring to Fig. 3, the hearth is designated g, the slag layer it, and layers of refractory material comprising a conductor of the second class are shown at in.

It will be observed that these layers of refractory material overlie and cover the ends of electrodes (Z, a and f. The furnace is of the general type shown in my aforesaid application, said furnace being designated 1, the arch thereof 2, and the refractory lining 3. The refractory lining 3 which is rammed between the bottom electrodes, and which, when the furnace is in operation is traversed by the current,consists of ordinary burned dolomite, bein mixed with tar as binding means. which serves in'a similar manner for the preparation of-basic Bessemer converters (Thomas converter) as for the bottoms Siemens-Martin-furnaces.

In the case of continuous current with three wires according to the connection in Fig. 2 of the accompanying drawing the central conductor is divided into two separate conductors Z Z, and carried to the bot.- tom electrodes d f, and the outer conductors m m are carried to the surface electrodes. In the case of a single phase alternating current for which the connection Fig. 2 is also applicable, the nodal point n of the machine is dissolved, and instead of the same, the metal bath is connected in circuit by means of the bottom electrodes, so that the nodal point is at the same time trans- .ferred into the metal bath itself; where it may perhaps more properly be termed, in this case, the nodal or neutral zone.

The heating of the metal bath proper, in addition to the increase of the strength of the current, can also, as already stated, be increased by increasing the electric resistance between the bottom electrodes. This is preferably effected in a furnace described in the prior specification No. 431,158 by ramming on to the bottom electrodes 0. mass usually employed for lining metallurgical furnaces. This lining consists of conductors This is the so called black mass of the second class. As soon as they become hot owing to the steel bath above them, being strongly heated by thevoltaic arcs, they also become conducting and if the current (as in the present application) is forced to pass from one bottom electrode to another, they form a heating resistance mass.

I claim:

I 1. In combination with an electric furnace comprising a group of upper electrodes and a group of lower electrodes, a polyphase, alternating, electric-current generator, and circuit forming connections therefrom to members of the groups of electrodes aforesaid, whereby alternating current may be passed through a bath of material in said furnace, a substantially neutral zone of the circuit being maintained in the bath itself.

2. In an electric furnace, a hearth. electrodes arranged to cause current to flow through the bulk of the material contained in said hearth, poly-phase alternating current producing means, and connections between said electrodes and said means arranged .to ermit the flow of current through various sections of said bulk of material, to vary with the phase, the current fiow being maintained independent of the consumption of energy in the respective phases.

' 3. An electric furnace comprising a hearth, electrodes projecting thereinto, a transformer cooperating with one of said electrodes, one terminal of the primary and secondary coils of said transformer being electrically connected to said electrode.

4. An electric furnacecomprising a group of upper electrodes, a. group of lower electrodes, refractory masses comprising a conductor of the second class overlying the lower electrodes and means for delivering current through said bath between members of difierent groups and between members of the same group.

5. A method of operating electric furnaces which comprises passing alternating current through a bath of material to be heated, maintaining a substantially neutral zone of the alternating current circuit in the bath itself.

6. A method of operating electric furnaces which comprises passing alternating currents of difiermg general intensities simultaneously through material to be heated.

T. A method of operating electric furnaces which comprises passing a primary alternating current between the respective members of a group of electrodes, and one or more other electrodes distinct from said group, and in further passing a secondary alternating current between the respective members of said group.

8. A method of operating electric .furnaces which comprises passing an electric current of one density between the respective members of a group of electrodes and one or more other electrodes distinct from said group, and in further passing an electric current of a second density between the respective members of said group.

9. A method of operating electric furnaces which comprises passing a voltaic-arcforming current of one density through material to be treated, and also passing current of greater density through a high resistance medium in contact with said material.

10. A method of operating electric furnaces which comprises heating the bath therein by passing dense poly-phase cur rents through the bulk of the bath and voltaic-arc-forming currents through the sur face thereof.

11. A method of operating electric furnaces which comprises heating the bath therein by establishing light arcs between sets of electrodes and simultaneously heating by resistance by means of currents of high density.

12. A method of operating electric furnaces which comprises subjecting material disposed in said furnace to light-arc-forming alternating currents and to alternating resistance heating currents while intensifying the action of said last mentioned currents by converting aportion of the relatively high tension energy thereof which would otherwise flow through said material at high tension, to relatively low tension but dense current. V

13. A method of operating electric furnaces which comprises subjecting material disposed in said furnace to light-arc-forming alternating currents in such manner as to form a substantially neutral zone directly in the bath of material being treated, and simultaneously subjecting said bath of material to the action of resistance-heating currents.

14. A method of operating electric furnaces which comprises subjecting material disposed in said furnace to light-arc-forming alternating currents in such manner as to form a substantially neutral zone directly in the bath of material being treated.

In testimony whereof, I aflix my signature in the presence of two witnesses.

HANS NATHUSIUS. Witnesses ERNST KA'rz, C. Bmsmc. 

